The h Bar

ok so you're only saying that all universes that exist must be logically consistent

which implies the laws of logic are independent of the universe itself?

@Mew I think it is the case, but we don't know the axioms

@Mew only logical inference

in which case there must be some mystical field that contains these logical inference rules and permeates into everything

amazing

Nothing mystical

9:14 AM

but I'm saying the rules can't come from nothing

as an analogy, if we say the sun attracts the moon

Something or nothing is some kind of structure

it can't just act at a distance

there must be a field

because the sun can't magically effect the moon otherwise

there must be a mediator

The existence of structures requires a notion of consistency

in the same way, I don't feel that the laws of inference can exist everywhere "just cos"

but you're now referring to the axioms of logic not the logical inference

@Mew Of course, but that's not what I'm saying

9:16 AM

why can't a universe be inconsistent though?

what stops it?

Q: Is four-current necessarily timelike?

0

In the spacelike case, there is a frame in which the charge density vanishes but current density does not. Additionally, the drift velocity of a free current would propagate superluminally. For this reason I would expect such a current to be impossible. In the lightlike case, the charge and curr...

electromagnetism

GR guys needed

It's like you're saying the world could have relied on something else then Peano's arithmetic but it would still be using the some logical inference, just different axioms

@Secret Got bitten last time I went GR...

I think logical consistency is an illusion

it is our way of seeing structure in our current universe

Just like numbers are illusions

@Mew But there are structures!

the universe is full of quantum fields, there are never really any discrete structures in the universe

yet we still invented counting

and we thought numbers we real

9:20 AM

How come? Numbers could easily be seen as some kind of equivalence class on qualia

but they are just our minds way of making sense of the world

@Mew A quantum field is a structure-full object

@G.Bergeron yes I'm giving an analogy

Structure does not have to be discrete

yes i'm talking about numbers

discrete numbers dont' really exist anywhere but our minds

because the universe is continuous

but our minds see things as discrete

9:21 AM

@Mew Ans your mind is not in this universe?

and we were tricked into thinking numbers exist

similarly

The question about GR and four currents is weird

we are tricked into thinking logical inference rules are real

it is just our minds way of making sense of things

@Mew Tricked by what?

but the universe doesn't care for sturcture in reality

just like it doesn't care for number

@G.Bergeron by our own minds way of simplifying thigns

9:22 AM

But there an element of the universe

our mind is a bunch of nuerons made to enhance surivval

I am not dualist

I'm saying the mind is part of the universe

let's talk about computers

Yes well this bunch of neurons figured out a way to emulate the number concept

correct

John Rennie

9:23 AM

Now this is the way to write an abstract:

arxiv.org/abs/1110.2832

my point is, the "number concept" isn't a real mapping to the universe

it is an approximatino at best

and similarly, our minds idea of "structure" is also just a simple concept that is only an approximation to the real workings of the universe

@JohnRennie LOOOOOLLLLLL

dualism has nothing to do with it

@Mew Ok then the approximate concept is really embeddable in the universe

embeddable?

9:25 AM

or whatever

a part of

yes

for example, take fingers

Q: Is four-current necessarily timelike?

This question is a trap

0

In the spacelike case, there is a frame in which the charge density vanishes but current density does not. Additionally, the drift velocity of a free current would propagate superluminally. For this reason I would expect such a current to be impossible. In the lightlike case, the charge and curr...

electromagnetism

fingers appear to be discrete

but really on the microscopic scale they are not

koolman

Hii @Mew

and this fools any animal into thinking discrete stuff exists

doesn't mean a property of the universe is that discrete is real though

koolman

9:26 AM

Could you come on physics.qandaexchange.com

@Mew So partial model captures nothing

it captures enough to survive

but not enough to knwo truth

Come on, this whole process would require some form of logical consistency in the universe so that surviving is not just sheer luck

Otherwise I don't see how evolution would be relevant

@koolman re-opened, please make the suggersted edits

koolman

@Mew thanks a lot

9:28 AM

"In the spacelike case, there is a frame in which the charge density vanishes but current density does not. Additionally, the drift velocity of a free current would propagate superluminally"

@G.Bergeron there does indeed appear to be logical consistency in our universe

but the key to my statement is "appear" and "in OUR universe"

we can't necessarily conclude it MUST be so in ALL universes

in my opinion

@Mew Appear implies is is my point

the fooling mechanism would need to be consistent so that it consistently fools you

it's not a fooling mechanism

@Mew Don't trash my nobel prize :(

Would be a cool name, no?

like i'm not saying the universe is conspiring to make us believe in numbers

but rather our minds just invented numbers to simplify what the mind saw

9:34 AM

Ok, forget the name, just the thing that makes it appears as so

and of course, the mechanism of human minds are similar

so of course all humans are going to comprehend the universe in a fiarly similar way

that is, one with "structure"

and "numbers"

@Mew Ain't that some kind of structure preserving map, if no structure was preserved the input is useless, if no structure is there to begin with, then the input is useless again

@G.Bergeron is there a number preserving map if the number of fingers and toes dont' change? Does this mean numbers are real? NO

We totally seized the chat room

yes structure appears to be conserved

9:37 AM

sorry

ty for apologzing

LOL

@Mew Sorry, but I don't get your point here

@G.Bergeron well you agree numbers aren't real right?

they are a tool our mind has created

" Burning at the stake is OK as long as you don't overdo it. I don't like my meat well done. " XD I starred it fast enough!

LOL

9:38 AM

@Mew Meh as much as an electron

It's also a tool/model

@G.Bergeron yep so numbers aren't real but we can easily be fooled into thinking they are real

because everything we look at appears discrete

even though on the micrscopic level, everything is continuous

@Mew Then I guess we disagree on the definition of being real

so evolutionarily we developed a way to understand numbers

in the same way we see structure

all around us

I mean numbers are as real as electrons will ever be

but this is also an illusion like numbers

something to help us but not a fundemantl truth of the universe

@G.Bergeron but electrons aren't real

they are in reality fields

not discrete particles

9:40 AM

Its not an illusion, there just might be some different "choice of gauge" but yeah.

Yeah well an electron is a field but my point remains

my point is a universe doesn't require discrete objects, despite it seeming on our scale that nearly every object is distinct from every other one

When is the last time you handled "continuous" object not using discreet symbols

humans however are evolved to see the discrete, because it allows us to process threats more easily

and thus we use "discrete" symbols because it is the way our mind has evolved to process information

Ok but then you're just saying that we are quotienting out some information and structure

so what, the point remains that structure there is

But any thought on the posta bout 4-currents?

Q: How many dimensions does electricity have?

16

My six year old daughter asked me this morning, 'how many dimensions does electricity have ?' What would be the best answer bearing in mind the age !?

electricity dimensions

9:45 AM

$J=\gamma\rho_0 (c, \vec{u})$ How can there be a frame where $\rho_0\gamma c=0$?

Left it as a comment, that is the problem i think, you can have space-like four-current, no?

Timelike would imply essentially a static charge, modulo some boost.

@Mew O wow, they deleted my comment. Guess not the right level, huh?

10:04 AM

@Secret now I'm curious

And why are some users pictures in the chat ar whitened

And I like your pictogram more than mine

Well, my comment is basically getting a 2D and a 4D maxwell equation post concluding that electroamgnetism is 3D, hence electity follows as it is a subset

@Secret how does a 6 year old get that tho?

Fair enough, I was arguing over there that the abstraction of electricity lived on cyclic graphs, it is 1D

:34008803 passed on or out? :p

lol either one

probably why it is deleted. But that's unusual cause comments are deleted often if they are disruptive, and I don't see how mine is disruptive

10:14 AM

Is that trump?

yeah

POTUS

miam

huh

A potus to me sounds like a weird african hybrid between an elephant and a hypoppotamus

yeah it's prounounced "P. O . T. U. S"

10:16 AM

"The following experiment is a simple one that can be tried at home. First pick up a ball in your hand and then release the ball above the ground. If you observe carefully you may see the ball moving closer towards the Earth. This is evidence of the mysterious gravitational force."

Really you spell it?

LOL

lol u like that one

@G.Bergeron i dunno how to pronounce POTUS just playing

I think there is an overlap in our humour style

yeah, see

Ok, this website ate through my sleep on the last to days. I never used the chat before that's the tipping point towards addiction

Danu

@ACuriousMind: chat.stackexchange.com/transcript/message/34008877#34008877

(from here: ams.org.emedien.ub.uni-muenchen.de/mathscinet-getitem?mr=877637)

11:06 AM

@Danu other source?

12:15 PM

hello

Hey there

how's life

Tough, today I misread my alarm and ran like hell to get ready and come to uni

I'm 1 hour early

I read the thing wrong

I'm sorry, that's terrible

Not a good few days I'm having

A: GR. Einstein's 1911 Paper: On the Influence of Gravitation on the Propagation of Light

12:23 PM

::shakes head in sympathy::

John Rennie

1:02 PM

The speed of light is frakking constant! OK!!

2

0

There is a lot of confusion about what exactly is meant by the speed of light in general relativity, so I think it’s worth examining this with some care. The issue turns out to be absolutely fundamental to general relativity. Special relativity Let’s start with special relativity. Although it’s...

lol

@JohnRennie You're the god of PSE

4

OMG

@JohnRennie I needed you last night!

I got in a fight over how to pronounce "Leicester"

So, how does one pronounce it?

user228700

Hey, I too got in a fight about that once! :-o Not even kidding.

The girl wasn't very happy about my thoughts on the matter :P

i always thought it was "lie - sester"

user228700

1:08 PM

I see..? :-P

but i've never heard it spoken, so

user228700

Hi heather :-) How's it going?

I say it "lie-chester" basically

She said "Lester"

gtg, bus stop awaits

fwiw, my mom says its lester

=)

user228700

^ That's literally the exact same thing I said! And the guy told me it was "lester". Weird o_O

1:10 PM

But she used to call "L'Hôpital's Rule" "Lahopitás Rule"

So idk

@heather I'll fight her on it

No one says "Lester city" for the soccer team

it's "Leichester city"

user228700

@BernardMeurer My teacher got super pissed about everybody mispronouncing that.

@JohnRennie What is up

You're the expert in British affairs

@BernardMeurer Why does @JohnRennie know so much about English people cheating on their spouses?

user228700

Oh, BTW, @BernardMeurer, why did u take back ur opinion about curries?

Daler Mehndi - Tunak Tunak Tun Video

@Jim LOL

@Kaumudi Simple, because this is the best thing India has ever made:

►

1:14 PM

@BernardMeurer Incorrect. India also made the kama sutra

user228700

@BernardMeurer ::Cringe-fest::

@Jim Have you ever attempted any kama sutra? That shit ain't human

@Kaumudi What? That is literally my favourite thing

user228700

:-P Seriously?

Well, not in the world, but definitely from India

They still wrote the book on sex. If you ask me, that's better than even the invention of sliced bread

user228700

1:15 PM

People play that so often here, it's not fun anymore.

Come on it's a fat man dancing and talking bullshit, what else is there in life?

user228700

There are other fat Punjabis talking bs that's super popular these days. The one u linked is still better, so yeah...

And the special FX are so good too

It's just a piece of art

user228700

x'D That's part of the cringe-fest.

user228700

Say, @BernardMeurer: When u say "curry", what are u thinking?

user228700

1:19 PM

I've always wondered what people who aren't Indians mean when they say "curry". Like there's only one type!

Well, I bet my bottom dollar you say "Apple" even though there are a variety of different kinds ;)

And in general I'm referring to whatever it is they serve at the Nepalese restaurant nearby

user228700

:-P But curry is so different! Who cares about apples?

@Kaumudi I think of a saucy dish that uses the curry spice and likely has chunks of delicious meat in it

user228700

Ah, I see. Bet @DanielSank thinks about it differently.

@Kaumudi Newton cared

user228700

1:21 PM

@BernardMeurer Okay. I've never had Nepalese before so I'm still just as confused as before.

user228700

Have u tried anything of the likes of this speciality:

In all honesty, since I don't speak Indian nor Nepalese, I though they were indian for a while, which was weird because I had never ever seen them do the classical indian nod, but I guessed maybe not everyone did it and left it alone

A few months later I noticed the place is called "Taste of Everest" which as it so happens is in Nepal

So my theory is that they are Nepalese

user228700

@BernardMeurer Ewww! Why would anyone want to taste icy rocks?

I've had that back in Brazil, bloody delicious

@Jim You're on a roll today aren't you? :P

user228700

1:24 PM

@BernardMeurer Ohh, okay. Your guess is prolly correct.

No. I'm on a roll every day

user228700

@BernardMeurer Yep. No arguments there. Best. Thing. Ever.

@Jim Hahahaha

user228700

Although, I'm just putting this out there, Indian is not always curry. Has anybody heard of Dosa?

Also, "Jim on a Roll": not as good a side dish as you might think

1:25 PM

@Kaumudi Is that a kind of curry? :P

user228700

:-P Noo. This:

@Kaumudi Well, that was obvious. Not every dish in India uses curry. Just like not every dish in my country uses maple syrup

user228700

Is there curry inside that bread?

user228700

@Jim Maple Syrup? U must be from Canada! :-P

user228700

1:28 PM

@BernardMeurer a. It's not bread b. Nope

Yup

@Kaumudi I think I might have had that

My neighbour cooked it for us once

@Kaumudi It's "I can't believe it's not bread"?

user228700

Ohh, cool.

user228700

:-P Hey, bread is pretty cool and all but I like Doss more than I like "curry".

user246160

1:30 PM

@BernardMeurer Indian is not a language :-P And @Kaumudi Isn't it cruel to post such tasty food pictures on chat? (I am hungry and I have nothing to eat other than biscuits :P) XD

user228700

Aw, I'm sorry man. What's for dinner?

user246160

No idea....something boring...like fish and rice

user246160

:-P

user246160

You ?

user228700

I usually have roti with some type of curry but today, well, not to annoy you even more, but PIZZAAA :-P

user246160

1:33 PM

Someone please suspend this girl here for one day XD ^

'and now we promote the coefficients to operators'

How do people go along with that when they do qft

user228700

@TheStackExchange :-P Nooooo

Yeah you solved Klein-Gordon, yeah you wrote the solutions as linear combinations, but who said those coefficients could not be operators? Who? BS!

user246160

@Kaumudi So, what pizza ? :-P

@bolbteppa Yeah, I'm so outraged about this issue that's obviously not put in proper context for me to really know what's going on!

user228700

1:35 PM

Dude, jhod. I don't want to aggravate u even more :-P In any case, I'm vegetarian so nothing exciting for u, I suppose.

@Jim have you made sense of why they do it? How did you rationalize it away? I mean, I tried everything to pretend it was okay, but it's not :p

I'm sorry, I don't know the specifics of the case that has enraged you. I recall when I took QFT in university, it all made sense, but it may be that you encountered a case that makes less sense

user246160

@Kaumudi Ok, I feel a little less jealous now :-D

user228700

:-)

user246160

Anyone here tried the dominos chocolate pizza ? Give your reviews @Kaumudi

user228700

1:41 PM

There's s chocolate pizza?!?!?

user228700

Nooooooooooo, what have I done?! >.<

@Jim I mean when you solve, say, the klein-gordon equation for exponential solutions, $e^{-i p \cdot x}$, then note the general solution is a linear combination of these exponential's, $\int d^4 p \delta(p_0^2 - \omega_0^2 ) a(p) e^{-i p \cdot x}$. Great. But now, lets promote the $a(p)$ to operators magically, and furthermore ones that obey some commutation relations.

user228700

DAMMIT. It's too late now :'-(

user246160

yep!!!

user246160

it just released a few days back

user246160

1:42 PM

@bolbteppa and you have a problem with this because.....?

user246160

looks like worms though

Because it's mental?

that's not a reason. That is just reiterating you think there is a problem with it. I got that. What is the reason you see a problem in it?

user228700

No, no, nooo :'-( Although, properly thinking about it, "Meh". It doesn't sound amazing. I'll definitely try it someday tho.

1:45 PM

Because you are taking a PDE, funding functions that solve it, and randomly involving operators in the whole thing out of nowhere.

user246160

Actually, yeah. I would rather prefer spicy pizzas with extra extra extra cheese XD @Kaumudi

user246160

Though I love the choco lava cakes :-P

user246160

@SwapnilDas yo!

@TheStackExchange Sure, but you folks have some 5 different main languages, and my concern wasn't guessing which one the Nepalese would be talking

user246160

@BernardMeurer 5 ? Are you kidding me ? :-P We have 22 main languages :-P

user246160

1:48 PM

Anyway, I understand your point :)

@bolbteppa it's not random. They are annihilation and creation operators

We speak on in Brazil and we already can't understand each other

Where did creation and annihilation operators even come from? Why are they creation and annihilation operators? Why are you writing a function as a linear combination of such complicated things?

user228700

@TheStackExchange :-P Yeah, same here.

A: How do I quantize a classical field theory

@bolbteppa It's been almost 4 years since I studied this last, so I may be a tad rusty. I recall there's a perfectly logical reason why this is needed and it has something to do with the terms of the field no longer meaning the same thing they do in CFT. However, I can't quite recall those reasons off-hand

I do have an answer of mine, but it doesn't really answer your question

4

First off, props for even knowing the proper use of the terminology. I dare say most middle-schoolers probably think classical field theory is about listening to Mozart in a meadow. Now, if I may start at the beginning... You seem to know this already, but I'll restate it for pedagogical reason...

2:02 PM

@Jim Yeah I know what you mean, they say something like that in just about every book, field doesn't mean the same thing etc..., but at least I found it very jarring to write a function solving a PDE as a linear combination of operators with special commutation rules, spent over a year trying to go along with it. Basically, there is a very cool understandable reason

if you study the 'occupation number formalism' of quantum mechanics and the 'principle of indistinguishability' motivating why we throw away coordinate vectors and 'one particle operators' acting on multi-particle wave functions acting on each wave function separately changing the stationary state,

how this immediately motivates the existence of creation-annihilation operators, and how you can predict your operators will look the way they do in terms of these, also. Basically that simple idea of writing a wave function as a linear combination of operators is very well motivated and not just something you can do because it can be done and so we go along with it! :p